Tausendfüßler Copula?

No. They were not "in copula" when the picture was taken. But it most likely is a pair, where the male is the one on top. When they do mate, the male climbes around so that their foremost segments meet feet to feet, thus pulling her head towards him, embracing it by his legs.

I'm not sure what species they are. Hard to tell from this picture. It looks like order Polydesmida though.

I think they haven't mated yet. I'm guessing the male rides on the female to be around when she is ready to be inseminated. I'm not a specialist on polydesmid millipedes. But I've seen such behavior in other millipede orders. It is also quite possible that he's somehow getting her into the right mode by striking and tapping her body in certain ways, or at least spraying her with pheromones. It's not something I've witnessed. I just think it would be evolutinary efficient if he did and, therefore, also very likely to be.